The Evolved Packet System (EPS) of the 3rd Generation Partnership Project (3GPP) is composed of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN), a Mobility Management Entity (MME), a Serving Gateway (S-GW), a Packet Data Network Gateway (P-GW or PDN GW), a Home Subscriber Server (HSS), Authentication, Authorization and Accounting (AAA) server of 3GPP, a Policy and Charging Rules Function (PCRF) entity and other supporting nodes.
FIG. 1a illustrates the architecture of the EPS system according to the related art. As shown in FIG. 1a, a MME is responsible for related works of the control plane such as mobility management, processing of the non-access layer signaling, and subscriber mobility management context; a S-GW is an access gateway device connected with the E-UTRAN, forwarding data between the E-UTRAN and the P-GW and responsible for buffering paging waiting data; a P-GW is a border gateway between the EPS and the Packet Data Network (PDN), and is responsible for implementing functions such as access of the PDN and forwarding data between the EPS and PDN.
In 3GPP, a corresponding PDN network can be found through an Access Point Name (APN). Generally, one connection from the UE to the PDN is called as an IP Connectivity Access Network (IP-CAN) session.
When a terminal moves, the P-GW will server as an anchor point of the movement of the terminal (as shown in FIG. 1b). Based on the system in FIG. 1b, the specific steps of the flow of the terminal handover (as shown in FIG. 1c), and forwarding data through the interface between the S-GWs are described as follows:
step 1c01, a wireless-side network element judges that it needs to initiate a S1-based handover;
step 1c02, the source wireless-side network element sends Handover Required to the source MME;
step 1c03, the source MME sends Forward Relocation Request message to the target MME;
step 1c04, the target MME initiates Create Session Request including information associated with the P-GW to the target S-GW;
step 1c05, the target S-GW returns Create Session Response message to the target MME; in this step, tunnel information such as tunnel identifier allocated by the target S-GW for establishing a tunnel between the target S-GW and the target wireless-side network element.
Step 1c06, the target MME requests the target wireless-side network element to execute the handover;
In this step, the tunnel information allocated by the target S-GW will be delivered to the target wireless-side network element.
Step 1c07, the target wireless-side network element responds to the target MME with Handover Request Acknowledgement message;
In this step, the target wireless-side network element creates UE context and reserves resources, the Handover Request Acknowledgement message includes the tunnel information allocated by the target wireless-side network element (which is herein allocated for establishing a tunnel between the target wireless-side network element and the target S-GW), and also needs to include the forwarding tunnel information between S-GWs.
Step 1c08, the target MME initiates Create Indirect Data Forwarding Tunnel Request to the target S-GW to establish a data forwarding tunnel between S-GWs;
step 1c09, the target S-GW returns to the target MME a Create Indirect Data Forwarding Tunnel Response including a forwarding tunnel identifier;
step 1c10, the target MME sends to the source MME a Forward Relocation Response message;
step 1c11, the source MME initiates Create Indirect Data Forwarding Tunnel Request, which includes the forwarding tunnel identifier, to the source S-GW to request for establishing a data forwarding tunnel between S-GWs;
step 1c12, the source S-GW returns a Create Indirect Data Forwarding Tunnel Response to the source MME;
step 1c13, the source MME sends a handover command to the source wireless-side network element;
step 1c14, the source wireless-side network element sends the handover command to the terminal;
at this moment, the downlink data received by the source network and sent to the terminal will be sent to the target network via the forwarding tunnel between S-GWs;
step 1c15, the terminal initiates a handover confirm message to the target wireless-side network element;
step 1c16, the target wireless-side network element notifies the target MME to perform handover;
step 1c17, the target MME sends a Forward Relocation Complete Notification message to the source MME;
step 1c18, the source MME returns a Forward Relocation Complete Acknowledge message to the target MME;
step 1c19, the target MME requests the target S-GW to modify the bearer information to include the tunnel information allocated by the target wireless-side network element; after the target S-GW receives the tunnel information, if the S-GW is relocated, the target S-GW sends to the P-GW a Modify Bearer Request message to the P-GW including the tunnel information allocated by the target S-GW;
in this step, upon receiving the tunnel information allocated by the target wireless-side network element, the target S-GW establishes the tunnel to the target wireless-side network element for the terminal for sending downlink data messages of the terminal, and this tunnel is called as a downlink tunnel. In step 1c06, upon receiving the tunnel information allocated by the target S-GW, the target wireless-side network element establishes a tunnel to the target S-GW for the terminal, which can be used to transmit uplink data messages of the terminal and is called as an uplink tunnel. The manner for establishing two network elements in each place of the text is similar, and thus will not be repeated here.
Step 1c20, if the S-GW is relocated, the target P-GW responds to the target S-GW with a modify bearer response. The target S-GW responds to the target MME with the modify bearer response;
step 1c21, the flow of deleting the source network session and releasing the forwarding tunnel is executed. This flow may be triggered by the source MME through a timer.
As can be seen, the prior art only considers adopting the anchoring manner to achieve continuity of services during the process of terminal movement, but this method of fixing anchor point causes a problem of circuitous paths of the data packets, thus aggravating transmission delay and bandwidth waste.
The above existing problems are essentially caused by the communality of address and identity of Transmission Control Protocol/Internet Protocol (TCP/IP). In order to solve these problems, many new mobility management technologies are proposed currently in the industry, and the essential conception thereof is subscriber identity and location separation technology. There is already a solution of Subscriber Identifier & Locator Separation Network (SILSN) in the related art, for example, host-based implementation such as Host Identity Protocol (HIP) technology, and router-based implementation such as Locator/ID Separation Protocol (LISP) technology, each of which contains many technologies for support. In these solutions, the Access Identifier (AID) of the terminal subscriber does not change during the movement process, and routing and forwarding of data messages are implemented by additionally allocating a Routing Identifier (RID) according to the location of the terminal.
FIG. 1d illustrates an architecture of SILSN. The network topology of the SILSN architecture is divided into an access network and a backbone network that do not overlap with each other in the topology relationship. The access network is located on the border of the backbone network, and is responsible for access of all terminals, while the backbone network is responsible for routing and forwarding of data messages between accessed terminals. In the networks, AID is used to indicate the subscriber identifier of the terminal, and it remains unchanged during the movement of the terminal; RID is used to indicate the locator allocated to the terminal by the network and is used in the backbone network. It should be pointed out that the identifier and the locator may have different names in different SILSN architectures, which should be regarded as equivalent.
In the SILSN architecture, the terminal may be one or more of mobile terminal, fixed terminal and nomadic terminal, for example, mobile phone, fixed phone, computer and server, etc.
In the SILSN architecture, the access network is used to provide two-layer (physical layer and link layer) access means, and maintain the physical access link between the terminal and the ASN.
In the SILSN architecture, the main network elements of the backbone network comprise:
An ASN, which is used to allocate a RID to the terminal, maintain the AID-RID mapping information of the terminal, register to the ILR (also called as registration) and inquire the RID of the terminal, and implement routing and forwarding of the data messages. The terminal has to access the backbone network via the ASN. The RID allocated by the ASN points to the local ASN, i.e., containing the address information of the ASN, and when the RID is used as the target address of a data message, the data message will be routed to this ASN.
A Common Router (CR), which is used to route according to the RID in the data message, and forward the data message with the target address being the RID.
An Identity Location Register (ILR), which is used to process registration, logoff and query of the RID of the terminal, store and maintain the AID-RID mapping information of the home subscriber terminal;
Optionally, the backbone network may further comprise:
A Packet Transfer Function (PTF), also called as a packet transfer function node, which is used to, after receiving a data message sent by the home subscriber terminal, inquire the RID of a correspondent opposite end according to the AID of the opposite terminal of the correspondent opposite end in the data message, encapsulate the RID in a header of the message, and then forward it to a general forwarding plane.
An Interconnect Service Node (ISN), which has interfaces connected with the common router, ASN and ILR, and is used to realize interconnection and intercommunication between two networks.
The above ILR, or ILR and PTF constitute the mapping forwarding plane of the backbone network, and the CR, or CR and ISN, constitutes the general forwarding plane of the backbone network.
Based on the network of SILSN architecture, since the access identifier and location of the terminal are separated, the terminal and the correspondent opposite end identify each other through the AID, which may be allocated for the terminal when assigning at the home subscriber server, for example it may be an IPV6/IPV4 address or IMSI or temporary identifier or NAI. The RID is used to realize routing and forwarding of data messages. When the terminal moves, the AID does not change so as to keep the communication relationship between the terminal and the correspondent opposite end, while the RID may be reallocated as the terminal moves so as to support the mobility of the terminal without any fixed anchor point, thus solving the problem of path circuitousness of the data packet.
When communication occurs in the SILSN architecture, the ASN should perform RID encapsulation and forwarding after receiving uplink data messages (i.e., data messages sent from the terminal to the correspondent opposite end). Specifically, the ASN inquires locally the RID of the correspondent opposite end, if the RID is inquired out, the RID of the correspondent opposite end as the target address and the RID of the terminal as the source address are encapsulated into a data message containing the AID of the terminal and the AID of the correspondent opposite end, which is then forwarded to the ASN which the correspondent opposite end accesses via the general forwarding plane. If the RID is not inquired out, the RID of the correspondent opposite end is inquired in the home ILR of the correspondent opposite end and is then stored locally. At this moment, the message may be encapsulated with the RID of the terminal and is then forwarded to the general forwarding plane via the mapping forwarding plane, or after the RID of the correspondent opposite end is inquired out, the ASN performs RID encapsulation and forwarding processing in the manner as adopted when the RID of the correspondent opposite end is inquired out locally. In the downlink direction, the ASN de-encapsulates the RID after receiving the data message sent from the general forwarding plane, strips out the RID therein and then sends the data message to the terminal.
As can be seen, in order to realize normal forwarding of the message, the ASN needs to allocate a RID for the terminal when the terminal accesses the ASN, registers the RID to the ILR to update the RID of the terminal in the ILR. The ASN also needs to maintain the AID-RID mapping information of the terminal and its correspondent opposite end to realize RID encapsulation of the message. In an example, for each terminal, the ASN maintains communication relationship information between the terminal and the correspondent opposite end, which is herein referred to as the opposite terminal information of the terminal and comprises the corresponding relationship between the AID of the terminal and the AID of the correspondent opposite end, for example, the opposite terminal information may be in the form of a correspondent opposite end list, which records the AIDs of all correspondent opposite ends of the terminal; the opposite terminal information may also comprise the AID-RID mapping information of the correspondent opposite end, i.e., the ASN collectively maintains the AID-RID mapping information of the correspondent opposite ends of all terminals, for example, the ASN stores a mapping routing table, which stores the AID-RID mapping information of the correspondent opposite ends of all terminals accessing the ASN. Of course, the ANS may also maintain for each terminal the AID-RID mapping information of all correspondent opposite ends of the terminal respectively. Wherein, the purpose of the ASN maintaining the correspondent end information is to determine what correspondent opposite ends the terminal has when the terminal has a handover, thereby sending the new RID of the terminal to the ASNs which the correspondent opposite end access according to the correspond opposite end information. After the ASNs which the correspondent opposite ends access complete update, the data messages sent from the correspondent opposite ends can be directly routed to the ASN to which the terminal moves. Before the ASNs which the correspondent opposite ends access complete update during the handover process, the source ASN needs to forward the message sent by the correspondent opposite end to the terminal to the target ASN.
However, the relate art has not proposed any corresponding solution for how to support identity and location separation of a terminal during a handover process of a communication system such as LTE in which the control plane is separated from the media plane, thereby avoiding circuitous routes.
In addition, during the handover process, the source ASN needs to send the maintained opposite end information to the target ASN, and the target ASN, after obtaining the opposite end information of the terminal from the source ASN, informs the ASNs which all correspondent opposite ends of the terminal access respectively to update the RID of the terminal, which causes a large amount of information (e.g., correspondent opposite end list) to be transmitted during the handover process.